Alkenyl succinic acids as antiwear agents



United States Patent O 3,382,172 ALKENYL SUCCINIC ACIDS AS ANTIWEAR AGENTS Warren Lowe, Berkeley, Calif., assignor to Chevron Research Company, San Francisco, Calif., a corporation of Delaware No Drawing. Filed May 18, 1966, Ser. No. 550,947

1 Claim. (Cl. 25242.7)

ABSTRACT OF DISCLOSURE Lubricating compositions having alkenyl succinic acids, wherein the alkenyl is straight chain having secondary attachment to the succinic acid moiety, of improved antiwear properties.

This invention concerns novel lubricating oil compositions containing carboxylic acid antiwear agents.

The mechanism of wear in an internal combustion engine has not been completely elucidated; however, wear can be broken down into at least three modes: adhesive, abrasive and corrosive. Adhesive is caused by metal-tometal contact between sliding surfaces; abrasive is caused by entrainment of particulate solids which score the surfaces; and corrosive is caused by attack of metal by water, acids or other corrosive materials. Various additives are included in the lubricating oil to minimize wear.

Pursuant to this invention, surprisingly good antiwear results are obtained by incorporating in an oil of lubrieating viscosity at least about mM./kg. of the oil composition of alkenyl succinic acids having an alkenyl group of from about 14 to 22 carbon atoms, wherein the alkenyl group has less than about 10 mole percent of terminal attachment to the succinic acid moiety. While the antiwear agents of this invention can be used in combination with a variety of detergents, they particularly find use with overbased detergents, e.g., overbased phenates.

The alkenyl succinic acids which find use in the compositions of this invention will for the most part have the following formula:

wherein R is a straight chain alkyl or alkenyl group and R is a straight chain alkyl group. By straight chain is intended that each carbon atom is bonded to not more than 2 carbon atoms, except for the carbon bonded to the succinyl radical. The total number of carbon atoms of R and R will be in the range of 13 to 21.

While for the most part R will be an alkenyl group, the alkenyl succinic acids used in this invention may be catalytically reduced with hydrogen to form the saturated product. Since no advantage is found in using the saturated product, and the preferred method of preparation yields the alkenyl compounds, usually the alkenyl succinic acid will be used.

While individual compounds may be used, usually mixtures will be used both as to homologs and isomers. Generally, as to any one single compound, less than about 10 mole percent of the single compound will be present in a mixture. As to any one homolog, less than about 40 mole percent will generally be present in any mixture. At least about 10 mole percent of each of the homologs in the C range for R +R +1 will be present (R +R having a total of from 14 to 19 carbon atoms).

Illustrative succinc acids which find use in the compositions of this invention, either individually or as members of mixtures include 2-hexadecenyl succinic acid,

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3-octadecenyl succinic acid, 4-tetradecenyl succinic acid, S-pentadecenyl succinic acid, S-eicosenyl succinic acid, S-nonadecenyl succinic acid, 4-hexadecyl succinic acid, Z-octadecnyl succinic acid, etc.

The oil compositions of the present invention may be of various types having special properties adapting them for particular applications. Thus, they may be lubricating oil compositions ranging from light machine and household oils to heavy lubricants for large internal combustion engines, including diesel engines. Lubricating oils which find use as base oils include such naturally occurring oils as naphthenic base, parafiin base, asphaltic base and mixed base lubricating oils. Other hydrocarbon lubricants include lubricating oils derived from coal products, synthetic oils, such as polymers of propylene, butylene, etc., aromatic hydrocarbons, etc. Other nonhydrocarbon oils include esters of organic and inorganic acids such as carboxylates, silicates and phosphates. Also, alkylene oxide and polymers thereof find use. Uusually, the succinic acid additives will be used with hydrocarbon oils.

The succinic acids find particular use with phenate detergent additives. The phenates are described in numerous patents. See for example US. Patent Nos. 3,194,- 761, 3,178,368, 3,036,971 and 2,989,461. For the most part, the phenates are sulfurized alkyl phenols which have either an equivalent amount of calcium present or an excess of calcium present, in the form of calcium carbonate or other derivative of carbonic acid. Other detergents which may find use either individually or in combination with the phenates are sulfonates and alkenyl succinimides of alkylene polyamines having alkenyl groups of at least about 50 carbon atoms and alkylene polyamine of from 2 to 6 nitrogen atoms.

The amount of succinic acid additive in the compositions of this invention will generally be at least 10 mM./ kg. and rarely exceed 0.1 weight percent of the composition. For the most part, the additive will be present in the range of about 15 to 200 mM./ kg. of the composition.

The detergents will generally be present in from about 1 to 10 weight percent of the composition, more usually from about 1 to 5 weight percent of the composition.

Other additives may also be present such as oiliness agents, dyes, oxidation inhibitors, etc.

The following examples are offered by way of illustration and not by way of limitation.

EXAMPLE A.ISOMERIZATION OF C1540 (NUM- BER OF CARBON ATOMS) CRACKED WAX OLEFINS TO INTERNAL UNSATURATION Twenty pounds of C1540 l-olefins is charged into a kettle and mixed with 2 /2 pounds of a silica-alumina catalyst (known under the trade name of Aerocat). Stirring is continued for one-half hour .to disperse the catalyst, and then 800 pounds of Q l-olefins is added. Heating is started, and the mixture is kept at 400 F. with stirring for three hours. Initially, the temperature of the reaction mixtures rises to 425 F. due to the heat of reaction. The completion of isomerization is followed by the disappearance of an infrared band at 910 cm." After completion of the reaction, the mixture is filtered, and the isomerized olefin is distilled under mm. pressure at 370 F. The distillation is complete when the kettle temperature reaches 575 F.

EXAMPLE I.ADDUCTION OF THE ISOMERIZED OLEFIN AND MALEIC ANHYDRIDE A kettle is charged with 510 pounds of isomerized C l-olefins and 100 pounds of maleic anhydride (a ratio of olefin to maleic anhydride of 2:1 moles). The mixture is purged with nitrogen, and the system is sealed and heated to 450 F. with stirring. The pressure in the system is about 25 p.s.i.g. due to vapors of maleic anhydride. The reaction is complete in about three hours, and the completion is determined by the disappearance of an infrared band at 840 cmr The excess olefin is removed by vacuum distillation.

The alkenyl succinic anhydride is readily hydrolyzed by heating the anhydride in water at a temperature of from about 160 to 20 F. for a sufficient time to effect hydrolysis.

In order to demonstrate the effectiveness of the lubricating oil compositions of this invention having the succinic acid additive, the compositions were tested in the Ruston Hornsby Engine Test. The Ruston Hornsby 2- cycle engine utilizes four piston rings. The four rings to be used in the test are weighed individually and each weight recorded, as well as the combined weight of the four rings. The rings are installed on the piston, the engine assembled and the run begun. At the end of 20 hours run time, the engine is stoped, disassembled, the piston rings removed and weighed, and the Weight loss determined. The engine parameter values are as follows: Speed: 400 r.p.-m.; air inlet temperature: 100 F.; water inlet temperature: 130 F.; water output temperature: 140 F.; fuel flow rate: 50 ml. per second; top cylinder oil flow rate: 26 drops per minute.

The run is carried out for two further periods of 20 hours each, each time the weight loss being determined. The results from the first 20 hours are ignored, since the wear results from this period are usually unreliable. Therefore, the weight loss over the other two 20-hour periods (40 hours) is determined as an average and increased by one-third to indicate the results from the 60 hours. The results are reported as a percent increase or decrease over the base oil. The base oil is run at about the same time to provide comparative results.

Not only were the alkenyl succinic acids having nonterminal attachment to the alkenyl group tested, but also alkenyl succinic acids having terminal attachment.

Using a 60 viscosity index SAE 30 oil having 188 mM./kg. of an overbased sulfurized phenate (20 alkalinity value) as the reference oil, 17.6 mM./kg. of the two different succinic acids was added. The following table indicates the results.

(l-C alkenyl) succinic acid 118 It is evident from the above results that quite surprisingly, the alkenyl succinic acids having internal attachment of the alkenyl group to the succinic acid group provide far superior wear protection than the terminally attached alkenyl succinic acids. That is, straight chain or normal alkenyl substituted succinic acids having internal attachment to the succinic acid group are far superior in providing wear protection than their closest isomer, the terminally attached alkenyl succinic acid.

As will be evident to those skilled in the art, various modifications on this invention can be made or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the following claim.

Iclaim:

1. An improved lubricating oil composition which comprises a compounded lubricating oil having in an amount sufiicient to reduce wear, an antiwear composition of the formula:

wherein R is a straight chain alkyl or alkenyl group and R is a straight chain alkyl group and the number of carbon atoms of R and R is in the range of 13 to 21, and from 1 to 10 weight percent of said lubricating oil composition of an alkaline earth metal phenate lubricating oil detergent.

References Cited UNITED STATES PATENTS 2,133,734 10/1938 Moser 25256 2,452,319 10/1948 Patterson et a1. 25256 X 2,741,597 4/1956 Oosterhout et al 25256 2,916,454 12/1959 Bradley et al 25242.7

DANIEL E. WYMAN, Primary Examiner.

W. H. CANNON, Assistant Examiner. 

